With the progress of semiconductor devices in recent years, measurement and inspection techniques for semiconductors have been increasingly becoming more important. A scanning electron microscope typified by a critical dimension-scanning electron microscope (CD-SEM) is a device which scans a sample with an electron beam, and detects secondary electrons emitted from the sample so as to observe a pattern formed on a semiconductor device and measure a length thereof. In such a device, in order to perform highly accurate measurement and inspection, it is necessary to appropriately set conditions of the device and thus to control trajectories of secondary electrons.
Among scanning electron microscopes, a CD-SEM measures a length of a pattern, and thus the stability of a primary electron beam becomes considerably important. On the other hand, regarding secondary electrons, it is desirable to selectively detect secondary electrons having desired information by controlling trajectories thereof. For this, there is the need for a mechanism which changes only trajectories of secondary electrons without changing a trajectory of a primary electron beam.
In a scanning electron microscope, as an example of the mechanism which changes only trajectories of secondary electrons without changing a trajectory of a primary electron beam, PTL 1 discloses a method of detecting secondary electrons having desired information by separating trajectories of secondary electrons from trajectories of primary electrons by using a deflector based on an orthogonal electromagnetic field.
PTL 2 discloses a method of controlling the extent of convergence of secondary electrons on the basis of lens action using electrodes, thereby improving detection efficiency of secondary electrons.